Agreed.
2. Buy that which is showing strength - sell that which is showing weakness. The public continues to buy when prices have fallen. The professional buys because prices have rallied. This difference may not sound logical, but buying strength works. The rule of survival is not to "buy low, sell high", but to "buy higher and sell higher". Furthermore, when comparing various stocks within a group, buy only the strongest and sell the weakest.
In general it is right, but somebody follow this rule will end up with buy at top and sell at the bottom. There is no better way to make you go broke faster. Finding what is still on the up trend and what is topped is very hard. If you can do that, congrats! You'd be a billionair with no time.